Smart City Digital Twin Framework for Semantic Indexing and Dynamic Modelling of 3D Buildings

Smart City Digital Twins (SCDT), including 3D representations of the urban environment, have gained ever-increasing attention from academic, public, and private sectors in the last years. Being faithful, dynamic, three-dimensional replicas of the cities, SCDTs realize concrete decision support systems to facilitate the work of urban planners and decision makers. Over the years, several municipalities have succeeded in producing 3D city maps, particularly useful in managing and planning the development of the built infrastructure. However, in most cases such representations are static replicas without any semantic enrichment and offer very limited interactive visualization and manipulation, thus inadequate to support what-if analysis. In this paper, the 3D city modelling and visualization framework embedded into the Snap4City Digital Twin platform is proposed. Each building is represented with multiple 3D versions, augmented with semantic information, and modelled as an individual entity by exploiting the KM4City ontology. Web-based 3D dashboards are used to present the urban twin and allow users to inspect, control and modify in real-time the 3D virtual environment in order to evaluate different scenarios for development of the urban spaces.